| Abnormalities, severe cracking, bumps, or missing areas in the accessory drive belt Abnormalities in the accessory drive system and/or components may cause engine RPM variations and lead to a misfire DTC. A misfire code may be present without an actual misfire condition. | Replace the drive belt. |
| Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout May lead to a misfire DTC. A misfire code may be present without an actual misfire condition. | Inspect the components and repair or replace, as required. |
| A loose or improperly installed engine flywheel or crankshaft balancer A misfire code may be present without an actual misfire condition. | Repair or replace the flywheel and/or balancer, as required. |
| Restricted exhaust system A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a DTC. Possible causes of restrictions include collapsed or dented pipes or plugged mufflers and/or catalytic converters. | Repair or replace, as required. |
| Improperly installed or damaged vacuum hoses | Repair or replace, as required. |
| Improperly installed or leaking charge air cooler tube | Repair or replace, as required. |
| Improper sealing between the intake manifold and cylinder heads or throttle body | Replace the intake manifold, gaskets, cylinder heads, and/or throttle body, as required. |
| Improperly installed or damaged manifold absolute pressure (MAP) sensor or intake air pressure temp (TMAP) sensor The sealing grommet of the MAP sensor should not be torn or damaged. | Repair or replace the MAP sensor and/or the TMAP sensor, as required. |
| Damage to the MAP sensor housing | Replace the intake manifold. |
| Worn or loose rocker arms The rocker arm bearing end caps and/or needle bearings should be intact and in the proper position. | Replace the valve rocker arms, as required. |
| Stuck valves Carbon buildup on the valve stem can cause the valve not to close properly. | Repair or replace, as required. |
| Excessively worn or mis-aligned timing chain | Replace the timing chain and sprockets, as required. |
| Worn camshaft lobes | Replace the camshaft and valve lifters. |
| Excessive oil pressure A lubrication system with excessive oil pressure may lead to excessive valve lifter pump up and loss of compression. | Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace the oil pump, as required. |
| Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages Coolant consumption may or may not cause the engine to overheat. | Inspect for spark plugs saturated by coolant. Inspect the cylinder heads, engine block, and/or head gaskets. Repair or replace, as required. |
| Worn piston rings Oil consumption may or may not cause the engine to misfire. | Inspect the spark plugs for oil deposits. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test . Perform cylinder leak down and compression testing to identify the cause. Repair or replace, as required. |
| A damaged crankshaft reluctor wheel A damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the damage. • Systems with electronic communications, DIS or coil per cylinder, and severe reluctor ring damage may exhibit periodic loss of crankshaft position, stop delivering a signal, and then re-sync the crankshaft position. • Systems with electronic communication, DIS or coil per cylinder, and slight reluctor ring damage may exhibit no loss of crankshaft position and no misfire may occur. However, a DTC P0300 may be set. • Systems with mechanical communications, high voltage switch, and severe reluctor ring damage may cause additional pulses and affect fuel and spark delivery to the point of generating a DTC P0300 or P0336. | Replace the sensor and/or crankshaft, as required. |
